Split-level frame buffer

Abstract

A single, split-level frame buffer for use in a color imaging system includes a plurality of pixels having a first resolution level. A plurality of bits are provided for each pixel so as to enable accurate pictorial imaging. The frame buffer includes pixels having a resolution level which is higher than the first resolution level. Pixels on the edges of objects being imaged are replaced by the higher resolution pixels to provide images wherein object edges have high-resolution while object interiors have moderate resolution. In using a single frame buffer, images having more than one level of resolution are generated which do not require separation and merging operations.

What is claimed is: 
     
       1. A single frame buffer for use in a color imaging system, said frame buffer comprising a plurality of pixels having a first resolution level and a plurality of bits per pixel, said plurality of pixels comprising a first group of pixels having a first characteristic and at least a second group of pixels having a second characteristic different from said first characteristic, said frame buffer further comprising pixel replacement means for replacing said second group of pixels with substitute pixels, said substitute pixels having a resolution level which is higher than said first resolution level. 
     
     
       2. The frame buffer according to claim 1, wherein said plurality of bits comprise a number of bits sufficient to represent pictorial images. 
     
     
       3. The frame buffer according to claim 1, wherein said second characteristic is that said second group of pixels are located along edges of objects being imaged. 
     
     
       4. The frame buffer according to claim 1, wherein some color values serve as an indicator of whether said pixel replacement means is to replace a pixel with said substitute pixels. 
     
     
       5. The frame buffer according to claim 1, wherein at least one bit of a color separation in a pixel location serves as an indicator of whether said pixel replacement means is to replace a pixel with said substitute pixels. 
     
     
       6. The frame buffer according to claim 1, said pixel replacement means comprising a pointer provided at a location of a pixel being replaced, said pointer providing an instruction to replace said pixel with said substitute pixels. 
     
     
       7. The frame buffer according to claim 1, wherein said pixel replacement means comprises a hash and a hash table, said hash being provided at a location of a pixel being replaced, said hash table storing pixel location and said substitute pixels according to hash table entries, said hash providing an index to said entries in said hash table. 
     
     
       8. The frame buffer according to claim 1, wherein said substitute pixels are arranged into scan line buckets, said pixel replacement means searching said scan line buckets for an appropriate bucket, said appropriate bucket including substitute pixels having a desired resolution higher than said first resolution level. 
     
     
       9. The frame buffer according to claim 8, wherein entries in said scan line buckets are sorted into raster order to facilitate retrieval as said frame buffer is imaged. 
     
     
       10. The frame buffer according to claim 1, wherein said pixel replacement means comprises a list of replacement colors and a mapping means providing the correspondence between the replacement colors and the said substitute pixels. 
     
     
       11. The frame buffer according to claim 10, wherein said list of replacement colors contains only two colors and said mapping means is a bitmap. 
     
     
       12. A method of color imaging using a single frame buffer, said method comprising providing said frame buffer with a plurality of pixels having a first resolution level and a plurality of bits per pixel, said plurality of pixels comprising a first group of pixels having a first characteristic and at least a second group of pixels having a second characteristic different from said first characteristic, said method further comprising replacing said second group of pixels with substitute pixels provided in said frame buffer, said substitute pixels having a resolution level which is higher than said first resolution level. 
     
     
       13. The method according to claim 12, including providing a number of bits per pixel sufficient to represent pictorial images. 
     
     
       14. The method according to claim 12, wherein said second characteristic is that said second group of pixels are located along edges of objects being imaged. 
     
     
       15. The method according to claim 12, wherein some color values serve as an indicator of whether said pixel replacement means is to replace a pixel with said substitute pixels. 
     
     
       16. The method according to claim 12, wherein at least one bit of a color separation in a pixel location serves as an indicator of whether said pixel replacement means is to replace a pixel with said substitute pixels. 
     
     
       17. The method according to claim 12, wherein said replacing includes providing a pointer at a location of a pixel being replaced, said pointer providing an instruction to replace said pixel with said substitute pixels. 
     
     
       18. The method according to claim 12, wherein said replacing includes providing a hash at a location of a pixel being replaced and providing a hash table, said hash table storing pixel location and said substitute pixels according to hash table entries, said hash providing an index to said entries in said hash table. 
     
     
       19. The method according to claim 12, wherein said replacing includes arranging said substitute pixels into scan line buckets and searching said scan line buckets for an appropriate bucket, said appropriate bucket including substitute pixels having a desired resolution level higher than said first resolution level. 
     
     
       20. The method according to claim 19, including sorting said scan line buckets into raster order to facilitate retrieval as said frame buffer is imaged. 
     
     
       21. The method according to claim 12, wherein said pixel replacing comprises providing a list of replacement colors and providing a mapping means providing the correspondence between the replacement colors and the said substitute pixels. 
     
     
       22. The method according to claim 21, wherein said list of replacement colors contains only two colors and said mapping means is a bitmap.